Process and apparatus for mining by retreat reaming

ABSTRACT

A process of mining a horizontal coal seam in an underground mine comprising first boring a hole in the middle of the seam while continuously removing the coal with an auger conveyor. Then after suitable penetration reaming wings on the conveyor are opened to span the full height of the seam. The wings have cutters on them so that as the apparatus is withdrawn the coal is broken and conveyed to the accessible face. The apparatus includes an advance mining head. A tubular enclosure for the conveyor carries the wings which are pivoted on longitudinally extending axes. A retracting movement of the shaft which drives the apparatus causes opening movement of the wings. Spiral ribs on the tubular enclosure engage the coal and urge the apparatus forwardly as it is rotated and resist rearward movement when the shaft is retracted. Doors between the wings and conveyor open to admit the cut coal into the conveyor and close to retain the coal on the conveyor. Flanges on the wings act to retain the coal. Rollers are carried by the wings to engage the coal and support the weight of the apparatus. Conveyor sections are attached to the shaft rearwardly of the reaming section. Propellers on the shaft and spiral vanes on the tubular enclosure form a transition conveying means between the reaming section and the rear conveyor sections.

United States Patent Mulvaney 1 Feb. 15, 1972 [54] PROCESS AND APPARATUSFOR MINING BY RETREAT REAMING Charles S. Mulvaney, 2211 GreenleafAvenue, Chicago, 111. 60045 221 Filed: May 5,1970 21 App1.No.: 34,789

[72] Inventor:

Primary Examiner-Ernest R. Purser Att0mey-Everett G. Clements ABSTRACT Aprocess of mining a horizontal coal scam in an underground minecomprising first boring a hole in the middle of the seam whilecontinuously removing the coal with an auger conveyor. Then aftersuitable penetration reaming wings on the conveyor are opened to spanthe full height of the seam. The wings have cutters on them so that asthe apparatus is withdrawn the coal is broken and conveyed to theaccessible face. The apparatus includes an advance mining head. Atubular enclosure for the conveyor carries the wings which are pivotedon longitudinally extending axes. A retracting movement of the shaftwhich drives the apparatus causes opening movement of the wings. Spiralribs on the tubular enclosure engage the coal and urge the apparatusforwardly as it is rotated and resist rearward movement when the shaftis retracted. Doors between the wings and conveyor open to admit the cutcoal into the conveyor and close to retain the coal on the conveyor.Flanges on the wings 'act to retain the coal. Rollers are carried by thewings to engage the coal and support the weight of the apparatus.Conveyor sections are attached to the shaft rearwardly of the reamingsection. Propellers on the shaft and spiral vanes on the tubularenclosure form a transition conveying means between the reaming sectionand the rear conveyor sections.

13 Claims, 17 Drawing Figures PAIENTEDFEB 15 I972 SHEET 2 BF 5 ATTORNEYPATENTEU FEB I 5 I972 SHEET 3 0F 5 mv mw IN VENTOR. CHARLES S. M VANEYATTORNEY SHEET t 0F 5 o In PATENTEBFEB 15 I972 INVENTOR. CHARLES S.MULVANEY PATENIEUFEB 15 I972 SHEET 5 OF 5 INVENTOR CHAR LES S. MULVANEYPROCESS AND APPARATUS FOR MINING BY RETREAT REAMING BACKGROUND OF THEINVENTION This invention relates to the underground mining of agenerally horizontally extending coal seam by a boring and reamingprocess which minimizes dust propagation. The apparatus used in theprocess may also be used for earth boring and reaming operations ofgeneral application. More particu larly the invention relates to theunderground mining of coal by boring and reaming using an apparatuscomprising a spiral or auger conveyor.

Auger mining of coal has been successful and economical in open pits andin hillsides where vertical clearance is available but it has not beenused generally where head room is limited.

No art disclosing mining coal underground by boring and reaming has beenfound.

The U.S. Pat. to Kandle, No. 2,839,271, issued June 17, 1958 shows atunneling machine comprising an auger which bores a horizontal holethrough the earth from one location and then reams the hole by means ofa reaming head fastened to the auger at a second location and then movedback to the first location.

Cannon et al., U.S. Pat. No. 3,220,494, issued Nov. 30, 1965 showsmaking a vertical hole from one gallery of a mine to another by drillingfrom an upper gallery to a lower one, then attaching a reaming head andreaming upwardly.

Forsyth, U.S. Pat. No. 3,280,416, issued Oct. 25, 1966 shows decoking atower by drilling upwardly, then expanding reaming cutters in a spaceabove the coke and reaming downwardly.

Wheeler et al., U.S. Pat. No. 732,479, issued June 30, 1903 shows anauger for forming a conical hole, the auger comprising pivoted endsections which are expanded to ream'the hole.

Various other patents show reaming apparatus for enlarging the bore ofavertical drilled hole by reaming cutters whiclcare expanded in the hole,and Shook, U.S. Pat. No. 2,847,189, issued Aug. 12, 1958 shows such anapparatus in which the hol is reamed by drawing the reaming cuttersupwardly.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention toprovide for the mining of coalin underground mines with only a smallamount of dust propagation.

It is another object to mine a seam of coal by forming a hole in saidseam, enlarging the blind end of said hole to approximately the fullheight of said seam and breaking away the coal from the enlarged spacetowards the accessible face of th seam while conveying the coal towardssaid face.

Another object is to provide a reaming and boring tool and auger ofspiral conveyor sections of small size whereby the mining operation maybe carried out by a small number of men in a confined space.

Another object is to provide for mining coal whereby no men would workat the place where the coal is being removed from the seam and no roofbolting, props or rock dusting would be required at this locating.

Another object is to mine a seam of coal by using a cylindrical drilledhole having a diameter substantially equal to the height of the seam,the arch action of the walls of the drilled hole providing a roof andbottom support which allow mining under weak and tender rock whichotherwise could not be mined conventionally.

In order to achieve these and other objects which will become apparentas the description proceeds I provide a drilling and reaming apparatuswhich may be used for drilling and reaming in the earth for variouspurposes but particularly for mining a horizontal seam of coal by boringa holes in said seam, conveying the bored coal to the accessible face ofsaid seam by an auger or spiral conveyor, then reaming the blind end ofthe hole out by spreading reaming wings and continuing the reaming ofthe coal seam toward the accessible face while conveying the coal tosaid face with the auger or spiral conveyor. The apparatus comprises aspiral conveyor having the front end thereof enclosed by a cylinder, thefront of the cylinder having cutting means and the wall of the cylinderhaving reaming wings pivoting on longitudinally extending pivot axes.The apparatus is rotated by a shaft which is slidable through the centerof the conveyor and connected by links to the reaming wings so thatretraction of the shaft will open the wings. Doors on the cylindricalenclosure underneath the reaming wings open by gravity to allow the coalcut by the reaming wings to fall into the conveyor and then close toretain the coal on the conveyor. Spiral ribs on the cylinder engage thecoal and urge the apparatus forwardly while the shaft is being rotatedand retracted to open the reaming wings and ream the coal. Flanges onthe wings retain the cut coal and direct it towards the conveyor.Propellers on the shaft and spiral vanes on the cylinder act as atransition conveyor between the reaming section and spiral conveyorsections attached to the shaft rearwardly of the reaming section.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1a is a side elevation of the rear ofthe apparatus in place in a mine shown in cross section;

FIG. lb is a side elevation of the front of the apparatus in place in acoal seam with the reaming wings expanded;

FIG. 2 is a rear elevation of the apparatus;

FIG. 3 is a plan view of the driving means and cross conveyor with thespiral conveyor sections removed;

FIG. 4 is a side elevation of the front of the apparatus on a largerscale with the reaming wings retracted;

FIG. 5 is a view like FIG. 4 with the reaming wings expanded;

FIG. 6 is a front elevation of the boring head;

FIG. 7 is a cross section taken on the line 77 of FIG. 4 in thedirection of the arrows;

FIG. 8 is a cross section on an enlarged scale taken on line 8-8 of FIG.4 in the direction of the arrows;

FIG. 9 is a fragmentary cross section taken on line 9-9 of FIG. 4 in thedirection of the arrows;

FIG. 10 is an elevation of FIG. 9 from the right;

FIG. 11 is a cross section taken on line 1111 of FIG. 5 in the directionof the arrows;

FIG. 12 is a cross section on an enlarged scale taken on line 'l2'12 ofFIG. 5 in the direction of the arrows;

FIG. 13 is a fragmentary section taken on line 13-13 of FIG. 12 in thedirection of the arrows;

FIG. 14 is a cross section taken on line l4l4 of FIG. 4 in the directionof the arrows;

FIG. 15 is a cross section taken on line l5-l5 of FIG. 5 in thedirection of the arrows; and

FIG. 16 is a cross section taken on line 16-16 of FIG. 5 in thedirection of the arrows.

DESCRIPTION OF THE INVENTION The mining apparatus 1 of the inventioncomprises a driving unit 2, conveyor section 3, a reaming section 4 andan advance mining head or section 5. The apparatus is shown as beingused in an underground coal mine for mining a seam 6 of coal byoperations conducted from an entry 7 adjacent the accessible face 8 ofthe coal seam. Conventional bolts 9 are shown as providing supports forthe roof of the entry.

The drive unit 2 is a conventional portable-type which may be set up inand readily moved to different locations in the entry 7. The unit 2comprises a bed 10 carrying rollers 11 supporting a carriage 12 havingchannels 13 engaging the rollers, whereby the carriage may be moved backand forth over the rollers by an advance and retreat drive 14 comprisinga power means 15 mounted on the carriage and driving a drum 16 on whichis wound a cable 17 anchored at each end to the bed 10. Also mounted oncarriage 12 is a power means 18 for rotating the boring apparatus bymeans of a driven shaft 19.

The driving unit 2 may be adjusted in elevation by hydraulicallyoperated extensible and retractable legs or jacks 20.

A portable rack 21 is positioned adjacent the driving unit 2 and isadjustable in elevation as indicated by dotted lines by hydraulicallyoperated legs or jacks 22. Additional spiral conveyor units 23 arestored on the rack in position to be attached to shaft 19 and spiralconveyor units 23 in the conveyor section of the boring apparatus.

A spiral conveyor unit 23 comprises a shaft 24 carrying a spiral blade25 and connection means 26 at each end, as many units 23 are connectedtogether as needed. The rearmost unit 23 is connected to driving shaft19 and the foremost spiral conveyor unit is connected to shaft 27 whichis square in cross section and is slidably received in bearings 28secured in spiral blade 29. Spiral blade 29 is secured to and surroundedby a tubular cylindrical enclosure 30. Enclosure 30 has a rearwardreaming section 31 and a forward or advance mining head or section 32.The rearward reaming section 31 is made of two thicknesses of metal, anouter shell 33 and an inner shell 34. The rearward section 31 is weldedto the forward section 32 at their adjoining ends 35.

Four reaming wings 36 form segments of the outer shell 33 and are hingedthereto for pivoting about longitudinally extending axes by hinges 37.The reaming wings have rearward edges 38 which slope forwardly andoutwardly when the wings are expanded or open and forward edges 39 whichare parallel to the axis of the shaft 27. Replaceable cutters 40 aresecured to the inner sides of the wings at the edges 38, 39. The cutters40 are received in recesses 41 in enclosure 31 when the reaming wings 36are in their closed positions.

In order to expand or contract the wings 36 arms 42 are pivoted to eachwing and to the front of shaft 27 by universal joints 43. Thus, onrelative rearward movement of shaft 27 with respect to enclosure 31 thewings will open and on relative forward movement of the shaft withrespect to the enclosure they will close. A pin 44 secured to each wing36 forms a pivot axis for the universal joint 43 associated with thatwing. A roller 45 rotates on each pin 44. The roller bears against thecoal and serves to support the apparatus. A ring 46 is secured to theinside of the forward end of enclosure section 31 to reenforce it, thering spanning the spaces occupied by reaming segments or wings 36. Ring46 comprises sectors 47 and 48 secured together so as to form pockets toreceive the pins 44.

Forming segments of the inner shell 34 are doors 49 positioned inwardlyof the wings 36 and between the flights of the spiral 29, as shown inFIG. 13. Doors 49 are freely pivoted on hinges 50 which extendlongitudinally. The arrangement is such that as the apparatus rotatesclockwise as viewed in FIGS. 8 and 12 the doors on the left and top opendue to the effect of gravity and the doors on the right and bottomclose. Thus coal scooped up by the reaming wings falls into the spiralconveyor through the open doors and is retained therein by the closeddoors. Offset stops 51 are secured to the edges of the doors tocooperate with the inner shell to hold them in closed position. Flanges52 on the inside of the reaming wings near the forward edge act toreenforce the wings and also direct the coal cut by the cutters 40 intothe spiral conveyor 29.

Openings 53 are formed in enclosure 32 to provide for the passage ofarms 42, it being noted that when arms 42 are operated to expand thewings they not only move outwardly radially but also movecircumferentially due to pivoting of the wings on longitudinallyextending axes. Suitable slots (not shown) are formed in the spiralconveyor 29 to provide for the passage of arms 42. Flanges 54 aresecured at one corner of the openings 53 to reenforce the corner and actas a guide and stop for the extension arms 42, which bear against theflanges with considerable force as the apparatus is rotated.

Since shaft 27 slides with respect to spiral conveyor 29 and is fixedwith respect to spiral conveyor sections 23 a gap between sections 23and conveyor 29 develops when shaft 27 is retracted in order to openreaming wings 36 and pull the apparatus to the rear. In order to providea transition conveying means between the conveyors 29 and 23 propellers55 are secured to shaft 27 and spiral vanes 56 are secured tocylindrical enclosure 31.

Spiral rib 57 is provided on cylindrical enclosure 31 to the rear ofreaming wings 36 and spiral rib 58 is provided on cylindrical enclosure32 in front of wings 36 to engage the coal around the borehole and urgethe apparatus forwardly when it is being rotatedvin the direction of thearrow 59 in FIGS. 11 and 12 and urge the apparatus rearwardly when it isrotated in the opposite direction.

The forward tapered end 60 of shaft 27 is received in a correspondingsocket in an end stop 61 secured to spiral conveyor 29 to take thethrust of the shaft as boring proceeds in a forward direction. A ring 62is secured to stop 61 and carries replaceable cutters 63. Otherreplaceable cutters 64 are secured to the leading edge of the enclosure32 and to braces 65 connecting ring 62 and enclosure 32.

A cross conveyor 66 receives coal from spiral conveyor 23 and deliversit to a suitable point.

In operation the driving unit 2 is set up in the entry and the boringapparatus is driven into the coal seam 6 halfway between the top andbottom by attaching shaft 27 to shaft 19 and then rotating the shaft inthe direction of arrow 59 by power means 18 while advancing the shaft bypower means 15, the spiral ribs 57 and 58 engaging the coal and alsoacting to advance the apparatus. Cutter means 64 and 63 break the coalduring this operation and spiral conveyor 29 conveys the mined coal backto the cross conveyor 66 which conveys it to a suitable destination.After boring proceeds a suitable distance the driving means 18 and shaft19 are disconnected from conveyor shaft 27, retracted, then connected toshaft 24 of a conveyor unit 23, then advanced and thereafterdisconnected, retracted, connected and advanced until the advance mininghead formed by cutters 64, 63 and associated structure is driven as deepas possible into the coal seam. During this operation the rollers 45 actto guide and bear the weight of the apparatus to counteract the tendencyof the head to drift downwardly.

When the desired penetration is reached the power means 15 is operatedto retract the boring apparatus or cause it to retreat while rotation inthe direction of arrow 59 is continued. Ribs 57 and 58 continue to urgethe apparatus forwardly or resist movement rearwardly and therefore thewings 36 are expanded by arms 42. Actually, relative longitudinalmovement between shaft 27 and tubular enclosure 30, on which the wingsare carried, induced by urging the shaft and enclosure in oppositedirections causes the wings to open regardless of whether only theshaft, the enclosure or both actually move in a longitudinal direction.

After wings 36 are expanded rotation of the apparatus in the directionof arrow 59 is continued and retraction or retreat of the apparatus isalso continued until the desired amount of coal is mined. Conveyor units23 are removed as retreat mining proceeds by manipulations similar tothose used in advance mining. During retreat mining the coal is conveyedto face 8 by the spiral conveyors and delivered to cross conveyor 66 inthe same manner as during advance mining. After mining is concluded atone location in the seam the driving unit 2 is moved laterally and theoperation is successively repeated to mine out the seam.

While the wings 36 are being opened the rate of rotation is caused to behigher than after opening and during retreat mining. In other words, theratio of rotation to retreat movement is caused to be higher during theopening of the wings than after the opening in order to effect thedesired opening at a point as far inside the coal seam as possible.Completion of the opening operation is made known to the operator by adrop in power requirements.

The size of the apparatus, particularly the size of wings 36 and arms 42is chosen so that the diameter of the initial hole will be aboutone-half or less than the height of the seam and the diameter of theenlarged hole will be about equal to the height of the seam. Ordinarilythe entry would be about 16- feet wide and the length of conveyor units23 and the head apparatus consisting of the reaming section and theadvance mining section about ten feet each to enable easy handling ofthese sections or units and assembly and disassembly of the apparatus.

It will be noted that in this method of mining all operations arecarried on at one underground location in the entry 7 at the face 8 ofcoal seam 6. Two locations, as suggested by the patents to Kandle andCannon et al. are not needed. The breaking of the coal takes place inthe interior of the seam so that dust propagation is minimized. Spiralrib 57 serves not only to affect movement of the apparatus but also actsas a stop to prevent transmission of dust outside of enclosure 31. Useof the reaming wings allows smaller units to be employed to mine thefull height of the seam than would be possible in ordinary auger miningthus allowing handling and assembly of the units in the restricted spaceof an underground mine. The curved, archlike nature of the walls of thehole produced by the apparatus provide better roof and bottom supportthan is provided when all the coal is cut away so mining under weak andtender rock is feasible which otherwise could not be minedconventionally.

The curved shape of each of the reaming wings 36 acts to direct the coalsmoothly into the conveyor while the flange 52 on each wing inhibits thecoal from escaping forwardly. The sloping rearward edges 38 of the wingsfacilitate retreat reaming and would cause collapse of the wings andprevent breakage if shaft 27 should be withdrawn faster than the coal isbeing mined. Doors 49 contribute to the efflcient gathering of coal byautomatically opening to admit coal to the spiral conveyor and closingto retain the coal in the conveyor.

If it should be desired to retract the reaming wings 36 and remove theapparatus a rotary movement in the reverse direction to that of arrow 59would be imparted to the apparatus while shaft 27 would be given aforward movement. This would cause relative movement between theenclosure 31 and shaft 27 in a direction to collapse the wings. Afterthe wings are collapsed the shaft 27 would be given a reverse orretreating movement while continuing rotation in a direction reverse tothat of arrow 59.

It will be understood that the surface of the coal where it engages theapparatus is shown in somewhat of an idealized condition. Spiral ribs 57and 58 engage or are embedded in the coal sufficiently to have ascrewing action in either a forward or reverse direction depending onthe direction of rotation but their engagement with the coal is alsosuch that they may have longitudinal movement with respect thereto,which occurs during retreat mining when the rotation tends to cause ascrewing action in an advancing direction but the actual movement of theapparatus is in a retreating direction.

lclaim:

1. A process of underground mining ofa seam of coal having a horizontalextension comprising forming a hole in said seam extending from anaccessible face thereof to an interior portion, inserting cutting meansinto said hole from said accessible face, removing coal from said seamby said cutting means to enlarge the diameter of said hole at saidinterior portion, loading a conveying means extending into said interiorportion with the coal removed by said cutting means, preventing the coalreceived by said conveying means from being unloaded into said interiorregion, conveying the coal to said accessible face and operating thecutting means to extend said interior portion of enlarged diametertowards said accessible face whereby substantially all the coal removedfrom the seam by the cutters is conveyed to the accessible face whilesaid interior portion is being extended towards said accessible face.

2. The process of claim 1 in which said conveying means is a spiralconveyor and the coal removed by said cutter from the seam falls ontothe spiral flights of said conveyor.

3. The process of claim 2 in which the cutting means and the conveyingmeans are part of a reaming tool having a boring head and the hole isformed by the boring head of the reaming tool.

4. The process of claim 3 in which the reaming tool has expandablereaming wings forming said cutting means and the forward portion of saidconveyor is rotated by a shaft slidable with respect thereto, comprisingurging the shaft in a rearward direction while urging the tool in aforward direction by spiral ribs engaging the wall of the hole to ex andthe wings.

5. T e process of claim 4 in which t e reaming tool has a tubularenclosure surrounding the forward portion of said spiral conveyor andcarrying doors, comprising causing the coal removed by said cutters tofall through the open doors onto the conveyor and retaining the coal onthe conveyor by closing said doors.

6. An earth-boring apparatus comprising a spiral conveyor having acontinuous line of spiral flights, reaming wings mounted for expansionat the external perimeter of said spiral flights rearwardly from thefront edge of said spiral flights, the forward portion of said spiralflights extending centrally and longitudinally with respect to saidreaming wings.

7. An earth-boring apparatus as in claim 6 in which a tubular member issecured to and surrounds the forward portion of the spiral conveyor andsaid wings are mounted externally of said tubular member.

8. An earth-boring apparatus as in claim 7 in which a centrally locatedshaft rotates the forward portion of said spiral conveyor and isslidable with respect thereto and there are means attached to the wingsand the shaft for expanding the wings on relative rearward movement ofthe shaft with respect to the tubular member.

9. An earth-boring'apparatus as in claim 8 in which doors are locatedinwardly of the wings, between the wings and the conveyor, said doorsopening to admit material cut by the wings into the conveyor and closingto retain material in the conveyor.

10. An earth-boring apparatus as in claim 9 in which spiral ribs on thetubular member are adapted to engage the earth surrounding the tubularmember and urge the apparatus forwardly as the apparatus is rotated in adirection to cut the earth whereby rearward movement of the member isresisted as the shaft is urged rearwardly to expand the wings.

1 1. An earth-boring apparatus comprising a spiral conveyor having aforward portion and a rearward portion, said forward portion carryingexpansible reaming wings, a shaft fixed to said rearward portion andlongitudinally slidable in said for-,

ward portion, said shaft being rotatably driven by said rearward portionand rotatably driving said forward portion, and means attached to saidwings and said shaft to expand said wings on the occurrence of relativelongitudinal movement between said forward portion and said shaft.

12. An earth-boring apparatus as in claim 11 in which the wings areexpanded by urging the shaft rearwardly, and including means engagingthe earth for urging the wings forwardly.

13. An earth-boring apparatus as in claim 11 in which a tubular membersurrounds the forward portion of said conveyor, the reaming wings arecarried by said tubular member and the means engaging the earth comprisespiral ribs on the tubular member.

1. A process of underground mining of a seam of coal having a horizontalextension comprising forming a hole in said seam extending from anaccessible face thereof to an interior portion, inserting cutting meansinto said hole from said accessible face, removing coal from said seamby said cutting means to enlarge the diameter of said hole at saidinterior portion, loading a conveying means extending into said interiorportion with the coal removed by said cutting means, preventing the coalreceived by said conveying means from being unloaded into said interiorregion, conveying the coal to said accessible face and operating thecutting means to extend said interior portion of enlarged diametertowards said accessible face whereby substantially all the coal removedfrom the seam by the cutters is conveyed to the accessible face whilesaid interior portion is being extended towards said accessible face. 2.The process of claim 1 in which said conveying means is a spiralconveyor and the coal removed by said cutter from the seam falls ontothe spiral flights of said conveyor.
 3. The process of claim 2 in whichthe cutting means and the conveying means are part of a reaming toolhaving a boring head and the hole is formed by the boring head of thereaming tool.
 4. The process of claim 3 in which the reaming tool hasexpandable reaming wings forming said cutting means and the forwardportion of said conveyor is rotated by a shaft slidable with respectthereto, comprising urging the shaft in a rearward direction whileurging the tool in a forward direction by spiral ribs engaging the wallof the hole to expand the wings.
 5. The process of claim 4 in which thereaming tool has a tubular enclosure surrounding the forward portion ofsaid spiral conveyor and carrying doors, comprising causing the coalremoved by said cutters to fall through the open doors onto the conveyorand retaining the coal on the conveyor by closing said doors.
 6. Anearth-boring apparatus comprising a spiral conveyor having a continuousline of spiral flights, reaming wings mounted for expansion at theexternal perimeter of said spiral flights rearwardly from the front edgeof said spiral flights, the forward portion of said spiral flightsextending centrally and longitudinally with respect to said reamingwings.
 7. An earth-boring apparatus as in claim 6 in which a tubularmember is secured to and surrounds the forward portion of the spiralconveyor and said wings are mounted externally of said tubular member.8. An earth-boring apparatus as in claim 7 in which a centrally locatedshaft rotates the forward portion of said spiral conveyor and isslidable with respect thereto and there are means attached to the wingsand the shaft for expanding the wings on relative rearward movement ofthe shaft with respect to the tubular member.
 9. An earth-boringapparatus as in claim 8 in which doors are located inwardly of thewings, between the wings and the conveyor, said doors opening to admitmaterial cut By the wings into the conveyor and closing to retainmaterial in the conveyor.
 10. An earth-boring apparatus as in claim 9 inwhich spiral ribs on the tubular member are adapted to engage the earthsurrounding the tubular member and urge the apparatus forwardly as theapparatus is rotated in a direction to cut the earth whereby rearwardmovement of the member is resisted as the shaft is urged rearwardly toexpand the wings.
 11. An earth-boring apparatus comprising a spiralconveyor having a forward portion and a rearward portion, said forwardportion carrying expansible reaming wings, a shaft fixed to saidrearward portion and longitudinally slidable in said forward portion,said shaft being rotatably driven by said rearward portion and rotatablydriving said forward portion, and means attached to said wings and saidshaft to expand said wings on the occurrence of relative longitudinalmovement between said forward portion and said shaft.
 12. Anearth-boring apparatus as in claim 11 in which the wings are expanded byurging the shaft rearwardly, and including means engaging the earth forurging the wings forwardly.
 13. An earth-boring apparatus as in claim 11in which a tubular member surrounds the forward portion of saidconveyor, the reaming wings are carried by said tubular member and themeans engaging the earth comprise spiral ribs on the tubular member.